Dear Lifehacker,
After finding someone else's cellphone outside last night in a thunderstorm, I was able to identify the owner by taking out the micro SD card and going through the pictures on my computer. After returning the phone, it occurred to me: On my smartphone, is my memory card protected by the device security? For example, I have an Android phone with fingerprint protection, but if someone removed my memory card, would they be able to see anything on it?

Signed,
Paranoid Android

Dear Paranoid,

Unfortunately, Android phones (and most others) don't yet ship with built-in, system-level encryption for data stored to the memory card. This doesn't mean that you don't have any hope of securing private files, though. While it's true that you can't secure the entire card completely, you can encrypt certain files, or even entire folders—basically anything that you want to keep safe from prying eyes in the event that your phone becomes lost or stolen. Android itself doesn't do this, but there are a number of apps available that can.

The majority of the apps that you'll be looking for will look something like the app pictured here. This app is called Lock Files, and it's available for free on the Android Market. Once you set a password, you can use this app to browse your SD card's folders, and choose anything you want to encrypt or "lock." One thing you'll need to remember with this, and every other app like it, is that once the file is encrypted, you need to delete the original. The apps work by making an encrypted copy of the original, then requiring a PIN to open your encrypted files.

Other similar apps include FileCrypt and MobiSafeFile. These apps, and many more like them, are available on the Android Market, and most of them are actually free. Just be sure the app is actually encrypting your files (it should say so).

It's not a perfect system, and ideally you could just flip an encryption switch in your phone's settings. The catch is that you'll have to pick and choose what's important enough to get encrypted, and what's "normal" enough to be left alone. If you were to encrypt your entire pictures folder, for example, you'd no longer be able to view them in Android's gallery app without decrypting them first, and that can get very tedious.

Sincerely,
Lifehacker

P.S. Got any tips for encrypting, hiding, or otherwise securing data on an Android device? Share it in the comments! Photo by Coline.